Connector for igniter plug



1957 w. A. BYCHINSKY 2,814,665

CONNECTOR FOR IGNITER PLUG Filed -Nov. 6, 1952 (IUNNECTUR FOR IGNITERPLUG Wilfred A. Bychinsky, Ann Arbor, Mich., assignor to General MotorsCorporation, Detroit, Mich, a corporation of Delaware ApplicationNovember 6, 1952, Serial No. 319,145

2 Claims. (Cl. 174-88) This invention relates to an electrical connectorand more particularly to an electrical connector especially suited foruse with an igniter plug in an internal combustion engine ignitionsystem. The qualities of the electrical connector structure of thisinvention which render it especially suitable for use in an ignitionharness as a lead for a sparking plug are its very high heat resistance,its resistance to deterioration andbreakage and its ability to providefor the expansion and contraction which results from the wiretemperature ranges to which such connectors are subjected.

The particular problem for which my invention provides a solution isthat which arises because of the very high temperatures encounteredadjacent internal combustion engines due to the large amounts of heatgiven off during their operation. Thus, my invention is particularlysuited for use on jet or gas turbine engines or gas turbine engineafterburners wherein extremely high temperatures are generated.

The ignition harness or spark plug connector structure immediatelyadjacent the internal combustion engine is subjected to very hightemperatures during the period of engine operation but at the same timeis also subjected to lower temperatures during the periods of. theengines idleness. Because of this wide temperature differential, it isessential that the conductor not only have a high heat resistance butalso that it be such as' to allow it to expand and contract withoutdamage and without breaking the electrical connection. At the same time,it is just as important that the connector structure have a certainamount of flexibility and have a high resistance to shock and vibration.Lastly, it is essential that adequate electrical insulation be providedto prevent short circuiting or flash over of the high voltage currentbeing conducted to the igniter plug. On conventional reciprocating typeinternal combustion engines which operate at relatively lowtemperatures, the insulation for the spark plug conductors generallyconsists of some elastic material such as rubber or the like, thismaterial having sufficient heat resistance to withstand thetemperaturesv encountered and at the same time providing the amount offlexibility, shock resistance and insulation required. Such insulationmaterial does not, however, have suflicient heat resistance for use onturbine engines or turbine engine afterburners operating at relativelyhigh temperatures, and it has therefore been proposed to use ceramic asthe igniter plug connector insulating material. Ceramics, however, haverelatively little flexibility and shock resistance and are particularlysubject to breakage. Moreover, continuous ceramic insulation isimpractical not only because of its low shock resistance and tendency tobreak but also because of its rigidity. On the other hand, discontinuousceramic insulation requires the use of some suitable supporting casingof a highly heat resistantmaterial such as metal, and when suchstructure is used, the good insulating qualities of the ceramic are lostbecause of the spaces which necessarily result between adjacentv piecesof the ceramic insulation.

'nited States Patent 2,814,665 Patented Nov. 26, 1957 It is an object ofthis invention to provide an igniter plug connector structure which isadequately insulated, has high heat resistance, high resistance to shockand breakage and which allows for expansion and contraction caused bywide temperature diiferentials. Another ob-. ject of the invention is toprovide an igniter plug connector structure which utilizes ceramicinsulation and thereby has a high heat resistance but which, at the sametime, has sufficient flexibility and shock resistance to preventbreakage and failure due to shock and engine vibration.

These and other objects are carried out in accordance with the inventionby the provision of a connector structure having a series of alignedtubular ceramic insulator members retained within a metal sleevesupporting member, each of said insulator members having a metal contactwithin its central bore and intermediate its ends, and conductor memberscovered with a ceramic insulation positioned within the insulatormembers to establish the electrical connection, the conductors andinsulator members being arranged in staggered relationship. By means ofsuch structure, the metallic conducting path is provided with adiscontinuous ceramic covering which furnishes electrical insulation asadequate as though the ceramic were continuous but at the same timeaflord the flexibility and shock resistance required. The connectorstructure of this invention may be straight or may be in the form of anelbow, the latter form being that required for most installationsbecause of the limited space available adjacent the turbine engine orafterburner to which the igniter is connected.

The invention, its objects and advantages will appear more clearly andprecisely from the following description of preferred embodiments aswell as in the accompanying drawing in which:

Figure 1 represents an igniter plug installation in a gas turbine engineafterburner and shows the connector structure of this invention in itsenvironment;

Figure 2 is a cross-sectional view of one embodiment of the invention;

Figure 3 is a bottom view of the igniter plug shown in Figure 1 butdrawn to larger scale; and

Figure 4 is a cross-sectional view of another embodiment of theinvention.

Referring now to the drawing, Figure 1 shows an igniter plug 6 mountedon the wall 8 of a gas turbine engine afterburner by means of a mountingpad 10. A fuel inlet pipe 12 is shown extending through the afterburnerWall to direct a combustible charge into the afterburner adjacent thespark gap of the igniter plug.

The igniter plug 6 consists of a center electrode 14 surrounded by aninsulator 16 which in turn is surrounded and supported by a metal shell18. A ground electrode 20 extends from the base of the shell into spacedrelationship with the end of the center electrode 14 to form a spark gaptherewith. The upper end of the igniter plug has secured thereto aconnector 22 embodying the present invention, this connectorestablishing electrical contact between the center electrode of theigniter plug and the source of the electrical energy of the ignitionsystem.

With reference now to Figure 2, the connector comprises a metalsupporting jacket 24, the interior of which is lined with a plurality ofaligned tubular insulator mem bers 26 and 28 through which extends instaggered relationship therewith a series of inner insulator members 29and 30 of smaller diameter and carrying conductors 32 and 34 inelectrical contact with each other to furnish a conducting path to theigniter plug 6.

For purposes of illustration the connector structure is shown asincluding only two outer insulator members and two inner insulatormembers and conductors; however, it is obvious that either end of theconnector can be lengthened by the use of additional insulator andconductor members arranged in the same relationship as that shown anddescribed.

In the particular embodiment shown by Figure 2, the metal supportingjacket is constructed in sections 36 and 38 secured together and to theigniter plug 6 by means of threaded joints 4i and 42 respectively.Welded joints are used at 44, 46 and 43 to secure the various parts ofthe individual metal sections 36 and 38 together. The tubular insulatormember 28 is fixedly secured within the metal jacket by means of anexternal annular shoulder 50 which engages an annular groove 52 on theinterior of the metal jacket. Gaskets, either of a metal such as copperor nickel or of a heat resistant cement composition such, for example,as a mixture of sodium silicate and asbestos is placed between the edgesof the shoulder 50 and the groove as shown at 54 and 55. In theembodiment shown, the connector is in the form of an elbow and thus thetubular insulator member 26 which is positioned at the connector elbowis also of an angular shape. This insulator member is retained withinthe jacket by means of an annular shoulder 56 which is held between theend wall 58 and the shoulder 60 of the jacket section 36 by a metalgasket 62 and a gasket 64 either of metal or of a heat resistant sealingcomposition of the type heretofore described.

The tubular insulator member 28 is provided with an internal annularshoulder 66 which supports a contact plug 68 for establishing electricalconnection between the end of the insulated conducting member 34 and thenext in line conducting member (not shown) which would be positioned inthe outer insulator bore shown at 70. The plug 63 is retained within theinsulator member by means of a pair of opposed flanges which engageopposite sides of the shoulder 66. In the case of the insulator member26, a contact plug consisting of a metal block 76 threadedly engaged bya screw member 78, the head of which abuts an internal shoulder of theinsulator member serves to establish electrical contact between the endsof adjacent ends of the conductors 32 and 34.

In the embodiment shown, the inner insulators 29 and 30 are in the formof a ceramic coating on the respective conductors 32 and 34. Each ofthese conductors is provided with flanges at either end in order toretain the ceramic coating and metal conductor as a unit and in order toai'ford a larger electrical contact area.

To provide the necessary heat and shock resistance and flexibilityneeded, the electrical contacts within the tubular insulators 26 and 28are made resilient by the use of spiral metal springs 88 and 90, one ofthese springs being interposed between one side of each of the contactplugs 68 and 76 and the adjacent end of the respective conductors 32 and34.

The terminal portion of most of the commonly used igniter plugs foraircraft reciprocating or gas turbine engines is the same or similar tothat shown by Figure 2 and consists of a ceramic sleeve 91, which isusually the top of the igniter plug insulator, at the bottom of which islocated the electrical contact 92 for the igniter plug centerwire. Theouter metal shell 18 of the plug concentrically surrounds the ceramicsleeve and is threaded as shown at 94 for the reception of the connectorstructure. The connectors of this invention are adapted for use withsuch a spark plug design, the lower end 96 of the tubular insulatormember 26 being substantially of the same dimensions as the top of theceramic sleeve 91 and the inner insulator-conductor member being sizedto fit into the sleeve 91 and make electrical connection with thecontact 92, the same staggered relationship being established betweenthe outer insulator 26, the ceramic sleeve 91 and the inner insulator 29as is established be tween inner and outer insulators in the main bodyof the connector.

In order to obtain maximum electrical insulation from the amount ofceramic used, it is preferable to locate the contact plugs 68 and 76 asclose as possible to the midpoint of the outer insulators since, in thismanner, the distance of the air path from the conductors 32 and 34 tothe metal sleeve 24 is at a maximum for the lengths of insulator membersused.

When the entire connector and igniter plug are assembled as shown anddescribed, the spaces between outer insulators are intermediate thebreaks in the inner insulation adjacent the contact plugs 68 and 76. Thelengths of the inner and outer insulators are, of course, sufficient toprevent a shorting-out over the air path from the conductors to themetal sleeve. Thus, while a discontinuous ceramic insulation is usd, ithas the excellent insulating qualities of a continuous ceramic body.

As stated previously, additional inner and outer insulators arranged instaggered relationship can be used to lengthen the connector. Electricconnection with the free end of the connector may be made by aconventional elastomer insulated conductor which is adapted to fit intothe bore of the last-in-line outer insulator and make contact with itsmetal center plug. This latter connection, may of course, be locatedaway from the high heat zone of the engine.

The threaded joint connector jacket shown in Fig. 2 is somewhatadvantageous in that it allows for easy assembly and disassembly.However, it has been found that the use of such threaded joints inignition harness has undesirable effects on radio reception andtransmission and from this standpoint, the screw jointed sleevestructure shown by Figure 2 is disadvantageous.

In order to eliminate such radio interference, in the preferredembodiment shown by Figure 4, the metal supporting jacket is a one pieceunit, the various portions of the jacket being jointed by welds as shownat 112 and 114. Likewise, the jacket 110 is welded to the outer shell116 of the igniter plug so as to eliminate the threaded joint at thispoint. Thus, with the structure shown by Figure 4, the only screw jointused is that at the free end 118 of the connector, this joint being usedto connect the ignition lead to the connector. While Figure 4 shows onlytwo series of inner and outer insulators, it is to be understood thatadditional series could be added if a longer connector is desired. Theouter insulators 120 and 122, inner insulators 124 and 126, conductingmembers 128 and 13!), contact plugs 132 and 134 and spring members 136and 138 are substantially the same in construction and location as thoseshown by Figure 2 and described with reference thereto. In order toimpart additional strength to the connector, a metal brace member 140having one end welded to the sleeve 110 and the other welded to theshell 116 of the igniter plug may be used.

The connectors of this invention employing inner and outer insulatorsarranged in staggered relationship so that the break in the outerinsulation is midway between the breaks in the inner insulation and viceversa afford means for utilizing all of the advantages of ceramicinsulation but at the same time provide the necessary shock resistanceand flexibility.

It is to be understood that, although the invention has been describedwith specific reference to particular embodiments thereof, it is not tobe so limited since changes and alterations therein may be made whichare within the full intended scope of this invention as defined by theappended claims.

I claim:

1. An electrical connector for an igniter comprising a metal jacket, aplurality of tubular ceramic insulators within and secured to saidjacket, each of said insulators having an electrical contact positionedwithin its bore intermediate the extremities thereof, a plurality ofelongated conducting members within said tubular insulators, each ofsaid conductors having a sleeve of insulating .5 material fixedlysecured thereto and extending between two of said contacts, and aresilient conducting member interposed between one end of each of saidconducting members and the contact adjacent thereto to establish aconducting path from a source of electrical energy to the igniter.

2. In combination with an igniter plug having a terminal portionincluding a ceramic sleeve insulator surrounded by a metal shell and anelectrical contact within said sleeve; a connector comprising anelbow-shaped metal jacket secured to said metal shell to form anextension thereof, a plurality of tubular ceramic insulators fixedlysecured Within said jacket to form a discontinuous elbow-shapedextension to said ceramic sleeve insulator,

each of said tubular insulators having a resilient electri- 15 ,87

References Cited in the file of this patent UNITED STATES PATENTS2,008,573 Blount July 16, 1935 2,081,503 Nowosielski May 25, 19372,173,766 Ramsay Sept. 19, 1939 Paulson Oct. 10, 1944

